'10 base -- 6-speaker stereo?

I recently bought a 2010 Fit base. From everything I've read, it should have a four-speaker stereo, vs. the 6-speaker in the Sport. But I count six speakers. Are there dummy grills on the dash, or do I indeed have the 6-speaker model? And if I do, does that mean I can add USB with a simple cable instead of something more elaborate and expensive?